A light activated collagen-flavin composite layer incorporating riboflavin is applied as treatment for infected lesions caused by bacteria and as the consequence of surgical procedures. These composites have also been found to be strong tissue adhesives that are effective in closing and sealing wounds, fixation of grafts/implants and anastomoses. Advantages include speed of closure, reduced infection due to the elimination of foreign matter, evidence of accelerated wound healing and the ease of use in complex surgery, especially when watertight seals, limited access or small repair size are important factors. The riboflavin in the collagen layer is exposed to light (e.g., light having a wavelength between 360-375 nm or 440-480 nm), decomposing the riboflavin to form reactive oxygen species (ROS). Strong crosslinks between the collagen composite and tissue results. In addition, similar exposures eradicate pathogens in the wound is eradicated resulting in a sterile wound. In other examples, the composite film may instead contain lumichrome or lumiflavin.